Vacuum image converter

ABSTRACT

A vacuum image converter has a vacuum flask containing an electrode device for reproducing an electron ray bundle released at the cathode upon an anode separated from the cathode. The converter is particularly characterized in that the electrode system is built into the flask as an element produced and adjusted outside of the flask.

United States Patent [191 Franz et al.

[111 3,846,654 [451 Nov. 5, 1974 VACUUM IMAGE CONVERTER [75] Inventors: Karl Franz, Erlangen; Hermann Christigau, Furth, both of Germany [73] Assignee: Siemens Aktiengesellschaft,

Erlangen, Germany [22] Filed: Mar. 8, 1973 [21] Appl. No.: 339,228

[30] Foreign Application Priority Data Mar. 15, 1972 Germany 2212579 [52] US. Cl. 313/94, 313/250, 250/213 VT [51] Int. Cl. H01j 31/50, l-10lj 39/00, l-l0lj 39/04 [58] Field of Search 313/94, 250; 250/213 VT 2,803,770 8/1957 Harkensee 250/213 VT 3,300,668 1/1967 Niklas 250/213 VT 3,617,791 11/1971 Franz et al 313/94 Primary Examiner-Ronald L. Wibert Assistant Examiner-Richard A. Rosenberger Attorney, Agent, or Firm-Richards & Geier [5 7] ABSTRACT A vacuum image converter has a vacuum flask containing an electrode device for reproducing an electron ray bundle released at the cathode upon an anode separated from the cathode. The converter is particularly characterized in that the electrode system is built into the flask as an element produced and adjusted outside of the flask.

3 Claims, 1 Drawing Figure VACUUM IMAGE CONVERTER This invention relates to a vacuum image converter having a vacuum flask containing an electrode device for reproducing an electron ray bundle released at the cathode upon an anode located at a distance from the cathode.

X-ray tubes of this type contain an electrooptically operating photocathode which releases electrons when struck by rays, such as X-rays, which are to be transformed in their frequency and intensity and the electrons of which are distributed corresponding to the distribution of the density of the rays in the ray bundle, for example, corresponding to an image. Then follows the electrode arrangement of the electron optics, which is so constructed that the electron image is represented upon the anode. To make the image visible the anode can be coated with a luminous substance which is lit by the electrons. The anode can be also the target of a television device. In that case the image converter is a part of a television receiving tube.

ln image converters and image amplifiers the vacuum flask contains the electrodes to a large extent as independent units which must be individually introduced and adjusted within the flask. However, there are also other constructions wherein a part of the electrodes is applied as coatings upon the walls of the flask. In such construction an adjustment step is also necessary, to correctly set the coated walls relatively to each other. At the same time it is necessary to carry out the already difficult vacuum tight relative adjustment of the parts of the flask.

An object of the present invention is to simplify the manufacture of vacuum image converters.

Other objects will become apparent in the course of the following specification.

in the accomplishment of the objectives of the present invention it was found desirable to produce and adjust the entire electrode system outside of the flask. Only then the entire system is enclosed in the flask. Then it is not necessary any more to combine the connecting procedure with the adjustment which provides an ideal optical axis only in the rarest cases due to the difficulty of vacuum tight connection of the parts which are either soldered or molten with glass blowing.

Since the construction is a simple one it is most advantageous to provide for a plurality of electrodes a common basic element which can consist of an electrically insulating material. Then the electrodes can be applied as coatings. Only those parts which provide difficulties during the manufacture of the carrier in one piece, must be produced as separate parts and inserted into the carrier or placed thereon. Usually there is a photocathode device which closes the cylindrical structural element on one side as a cover. The side opposite the cathode is constituted by the anode arrangement upon which the electrons are represented as small units. The anode is the bottom of the structure. An electrode located directly in front of this electrode and substantially parallel thereto is inserted in the simplest way as a separate part upon this bottom and is fixed by gluing or the like.

As material for the part used as the carrier it is very advantageous to use vacuum tight plastics. Then the shaping can take place either by chip removal or by pressing and casting etc. Parts of plastics receive already during their manufacture a refined, namely, a

very smooth outer surface without any additional treatment, as opposed to metals, whereby field emissions are suppressed to a large extent. Plastics have also the advantage that they can be welded among themselves or glued with metals and other materials. As plastics can be used polyimides or polysulfons, particularly polyarilsufons, since they are sufficiently vacuum tight during heating as well as in operation. The same plastic materials can be also used as glues.

However, other electrically insulating materials can be also used as the carrier of electrodes due to their good vacuum firmness, as for example, glass or ceramics. These materials have the advantage that the electrode arrangement can be set and adjusted outside of the vacuum flask and only then inserted. However, due to their mechanical properties they are more difficult to treat and to handle than the above-mentioned plastics.

in these devices mostly metal layers are used as electrically conducting layers, such as those of aluminum, chromium or chromium-nickel, which are applied by steaming. However, other application methods can be also used, as, for example, cathode spraying, electrolysis, poyrolysis etc. Conducting lacquers and coatings are also useable as long as they conform to requirements of the high vacuum of the image converter tube.

While the above-described examples refer substantially to a single structural element covering the system, it is also possible with advantage to operate with two part carriers which are joined when the flask is open. One of the two structural parts can then at the same time be a part of the flask and the second part can be applied upon the first part vacuum tightly after the adjustment. This has the advantage over the usual construction that the adjustment of the individual structural elements is more precise.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing the sole FIGURE of which shows by way of example only, a section through an X-ray image converter along its longitudinal axis.

The drawing shows a vacuum tube 1 consisting of two pot-like parts 2 and 3 of glass. The parts 2 and 3 have adjacent edges carrying flanges 4 and 5 of vacan or some other suitable melting alloy. The flanges lie one on top of the other and they are vacuumtightly welded at their outer edge 6. The flask 1 contains a cup-shaped part 7 serving as a carrier and consisting of polyimide. The shape of the part 7 is substantially that of the flask l; at its bottom is an oppositely extending part 8 constituting the actual anode. A part 9 placed in the groove 10 at the bottom of the part 7, constitutes the electrode mounted in front of the anode. The part 9 is glued in the groove 10 with polyimide lacquer, and so is the side extension 11 to the extension 12 of the flange 5 and, as well as the projection 13 of the cap 14 to the upper end of the part 7. The parts 7, 9 and 14 have a wall thickness of 1 mm, so that in case of a diameter of 300 mm they are sufficiently stable.

This construction constitutes the electrode arrangement which is produced in that a cap 14 having the shape of a section of a sphere receives a luminous layer 15 consisting of activated cesium iodide steamed on in high vacuum. The further layer 16 is steamed on in the usual manner after the completion of the flask; it consists of antimony which has been activated by cesium metals. The electrical connection takes place by a steamed on side metal layer 17 consisting of aluminum and having a thickness of 500 mg. The electrodes 18 and 19 as well as the coatings 20 and 21 of further electrodes and of the anode 8 also consist of steamed on aluminum layers with a thickness of 500 mu. At the end of the anode there is the known luminous screen 22 mounted upon a support 23 consisting of a glass plate 1 mm thick. The support also carrier a luminous layer 24 consisting of zinc-cadmium-sulfide activated with silver and having a thickness of 7a. Extending toward the interior of the flask is an electrically conducting covering 25 which consists of aluminum and is 200 mp. thick.

The electrical supply of the image converter takes place in the known manner through contacts 26 to 30, whereby between contacts 26 and 27 100 v. are provided, between contacts 27 and 28 300 v., between contacts 28 and 29 35 kv and between contact 29 and the connection 30 of the anode 8 a voltage of 25 kV is supplied.

When X-rays pass through the inlet window 31 light is produced in the luminous layer 15. This light releases electrons in the layer 16 which are diminished by voltages applied to electrodes 18, 19, 20 and 21 and are reproduced upon the luminous screen 22. They appear there as diminished light visible image with intensity distribution provided in the cross-section of the X-ray bundle. The image can be examined in the usual man- 4 ner by magnifying optics, it can be photographed or filmed, or received and further treated in a television process.

What is claimed is:

l. A vacuum image converter, comprising a vacuum flask, a cathode within said flask for releasing an electron ray bundle, an anode within said flask and spaced from said cathode for receiving said electron ray bundle and an electrode system actuating said bundle of electrons and said vacuum image converter further comprising a carrier disposed within said vacuum flask consisting of an electrically insulating substance, said electrode system comprising a plurality of electrodes located between said cathode and said anode and mounted as electrically conducting coatings upon said carrier, said carrier having the shape of a pot with a bottom enclosing the anode and a top constituting a cover carrying said anode.

-2. An image converter according to claim 1, wherein said electrode system comprises an electrode located in front of the anode, the last-mentioned electrode consisting of a plastic material and being glued concentrically upon the inner walls of said carrier.

3. An image converter according to claim 1, comprising a luminous screen and a photo-cathode layer, and a carrier consisting of a plastic material and located opposite the anode. 

1. A vacuum image converter, comprising a vacuum flask, a cathode within said flask for releasing an electron ray bundle, an anode within said flask and spaced from said cathode for receiving said electron ray bundle and an electrode system actuating said bundle of electrons and said vacuum image converter further comprising a carrier disposed within said vacuum flask consisting of an electrically insulating substance, said electrode system comprising a plurality of electrodes located between said cathode and said anode and mounted as electrically conducting coatings upon said carrier, said carrier having the shape of a pot with a bottom enclosing the anode and a top constituting a cover carrying said anode.
 2. An image converter according to claim 1, wherein said electrode system comprises an electrode located in front of the anode, the last-mentioned electrode consisting of a plastic material and being glued concentrically upon the inner walls of said carrier.
 3. An image converter according to claim 1, comprising a luminous screen and a photo-cathode layer, and a carrier consisting of a plastic material and located opposite the anode. 